U.S. patent application number 10/564108 was filed with the patent office on 2007-03-29 for method for making polyolefins having internal double bonds.
Invention is credited to Vincenzo Busico, Roberta Cipullo, Abbas Razavi.
Application Number | 20070073013 10/564108 |
Document ID | / |
Family ID | 33442859 |
Filed Date | 2007-03-29 |
United States Patent
Application |
20070073013 |
Kind Code |
A1 |
Razavi; Abbas ; et
al. |
March 29, 2007 |
Method for making polyolefins having internal double bonds
Abstract
The invention provides a method for the production of a
non-linear polyolefin, which method comprises: (a) providing a
polyolefin having a ratio of internal to terminal double bonds of
at least 1:1 and; (b) forming a non-linear polyolefin from the
polyolefin provided in step (a).
Inventors: |
Razavi; Abbas; (Mons,
BE) ; Busico; Vincenzo; (Napoli, IT) ;
Cipullo; Roberta; (Napoli, IT) |
Correspondence
Address: |
FINA TECHNOLOGY INC
PO BOX 674412
HOUSTON
TX
77267-4412
US
|
Family ID: |
33442859 |
Appl. No.: |
10/564108 |
Filed: |
July 6, 2004 |
PCT Filed: |
July 6, 2004 |
PCT NO: |
PCT/EP04/51369 |
371 Date: |
November 28, 2006 |
Current U.S.
Class: |
526/126 ;
526/127; 526/160; 526/170; 526/351; 526/352; 526/943 |
Current CPC
Class: |
C08F 110/06 20130101;
C08F 10/00 20130101; C08F 255/02 20130101; C08F 4/65912 20130101;
C08F 10/00 20130101; C08F 290/04 20130101; C08F 290/042 20130101;
C08F 4/65908 20130101; C08F 110/02 20130101; C08F 110/02 20130101;
C08F 2500/09 20130101; C08F 110/06 20130101; C08F 4/65927 20130101;
C08F 2500/20 20130101; C08F 2500/17 20130101; C08F 2500/20
20130101; C08F 2500/09 20130101; C08F 2500/17 20130101; C08F
2500/15 20130101 |
Class at
Publication: |
526/126 ;
526/127; 526/160; 526/170; 526/351; 526/352; 526/943 |
International
Class: |
C08F 4/06 20060101
C08F004/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 9, 2003 |
EP |
03102060.5 |
Claims
1-16. (canceled)
17. A method for the preparation of an olefin polymer having a
ratio of internal to terminal double bonds of at least 1:1
comprising: (a) providing a catalyst system comprising a
metallocene catalyst component characterized by the formula:
R''(Cp)(Cp')(MQp) wherein: Cp comprises a substituted
cyclopentadienyl group having at least one substituent on the
cyclopentadienyl group which is positioned at a location distal to
the bridge; (Cp') comprises a fluorenyl group which is
unsubstituted or substituted at least one of the three and six
positions of said fluorenyl group; R'' comprises a structural
bridge imparting stereo rigidity to the catalyst component; M is a
metal atom from Group IVB, VB or VIB of the periodic table; Q is a
hydrocarbon group having from 1 to 20 carbon atoms or is a halogen,
and P is an integer equal to the valance of M minus 2; (b)
contacting said catalyst system in a reaction zone with at least
one olefin monomer which is present in a diluent in a concentration
of less than 3 mol/L, under polymerization conditions at a
temperature within the range of 20-90.degree. C. effective to
polymerize said olefin monomer to provide a polyolefin having a
ratio of internal to terminal double bonds of at least 1:1; and (c)
recovering said polyolefin from said reaction zone.
18. The method of claim 17 wherein said olefin monomer comprises
ethylene or propylene wherein said olefin polymer is a polyethylene
homopolymer or copolymer, or a polypropylene homopolymer or
copolymer.
19. The method of claim 18 wherein said olefin monomer comprises
ethylene and said polymer is an ethylene homopolymer or an ethylene
copolymer.
20. The method of claim 19 wherein said ethylene monomer is
contacted with said catalyst system along with a comonomer of
butene or hexene to produce an ethylene copolymer.
21. The method of claim 18 wherein said monomer comprises propylene
and said polymer is a polypropylene homopolymer.
22. The method of claim 17 wherein said fluorenyl group Cp' is
substituted with at least one substituent in at least one of the 3
and 6 positions and said cyclopentadienyl group Cp is substituted
with a substituent which is bulkier than the substituent on the
fluorenyl group.
23. The method of claim 17 wherein said cyclopentadienyl group Cp
is substituted at the distal position with a substituent selected
from the group consisting of n-Pr, i-Pr, n-Bu, t-Bu and
Me.sub.3Si.
24. The method of claim 23 wherein said fluorenyl group Cp' is
unsubstituted.
25. The method of claim 23 wherein said fluorenyl group Cp' is
symmetrically substituted with a substituent which is less bulky
than the distal substituent of the cyclopentadienyl group Cp.
26. The method of claim 25 wherein said fluorenyl group Cp' is
substituted at the 3 and 6 positions.
27. The method of claim 17 wherein said R'' is selected from the
group consisting of an isopropylidene group, a diphenyl methylene
group, an ethylene group, and a dimethyl silyl group.
28. The method of claim 27 wherein said metallocene catalyst
component comprises an isopropylidene (3t-BuCp) (fluorenyl) ligand
structure.
29. The method of claim 17 wherein said polymerization is carried
out to provide a polyolefin having a ratio of internal to terminal
double bonds of at least 2:1.
30. The method of claim 17 further comprising reacting said
polyolefin produced in subparagraph (b) to produce a nonlinear
polyolefin.
31. The method of claim 30 wherein said nonlinear polyolefin is a
cross-linked polyolefin.
32. The method of claim 30 wherein said nonlinear polyolefin
exhibits long chain branching.
33. The method of claim 17 wherein the polyolefin recovered from
said reaction zone in subparagraph (c) is transferred to a second
reaction zone in series with said first reaction zone and further
comprising reacting the said polyolefin in said second reaction
zone to produce a nonlinear polyolefin.
34. The method of claim 33 further comprising functionalizing said
polyolefin in said second reaction zone by the reaction of said
polyolefin with a functionalizing agent in said second reaction
zone.
35. The method of claim 34 wherein said functionalizing agent
introduces polar groups at internal double bonds of said
polymer.
36. The method of claim 35 wherein said polar groups are selected
from the group consisting of carboxylic acid groups, acrylic
groups, acrylate groups and carboxylic acid ester groups.
Description
[0001] The present invention concerns a method for producing linear
polyolefins having internal double bonds. The invention is
especially effective when applied to polypropylene and
polyethylene. The invention also relates to a method for producing
non-linear polyolefins and functionalised polyolefins, particularly
polypropylenes and polyethylenes, from the linear polyolefins
having internal double bonds. Further, the invention relates to
polyolefins, particularly polypropylenes and polyethylenes produced
using the methods of the invention and to uses thereof.
[0002] Polyolefin resin such as polypropylene resin is used in a
variety of different applications. However, polypropylene resin
suffers from the problem of having a low melt strength, which
restricts the use of polypropylene in a number of applications
because the polypropylene is difficult to process. It is known in
the art to increase the melt strength of polypropylene, for example
by irradiating the polypropylene with an electron beam. It is known
that electron beam irradiation significantly modifies the structure
of a polypropylene molecule. The irradiation of polypropylene
results in chain scission and grafting (or branching), which can
occur simultaneously. Up to a certain level of irradiation dose, it
is possible to produce from a linear polypropylene molecule having
been produced using a Ziegler-Natta catalyst, a modified non-linear
polymer molecule having free-end long branches, otherwise known as
long chain branching (LCB). However, the properties are not
significantly improved.
[0003] It is desirable also to produce cross-linked polyolefins
from linear polyolefins because of their desirable properties such
as increased durability and adaptability. For example, U.S. Pat.
No. 5,554,668 discloses a process for irradiating polypropylene to
increase the melt strength thereof. An increase in the melt
strength is achieved by decreasing the melt flow rate, otherwise
known as the melt index.
[0004] It is known to make cross-linked polymers from linear
polymers using an agent to create radicals. Radicals in different
polymer chains then combine to form a `bridge` or `cross-link`.
Suitable agents include peroxide or ionising radiation, such as
gamma radiation.
[0005] EP-A-0520773 discloses an expandable polyolefin resin
composition including polypropylene optionally blended with
polyethylene. In order to prepare a cross-linked foam, a sheet of
expandable resin composition is irradiated with ionising radiation
to cross-link the resin. The ionising radiation may include
electron rays, at a dose of from 1 to 20 Mrad. It is disclosed that
auxiliary cross-linking agents may be employed which include a
bifunctional monomer, exemplified by 1,9-nonanediol
dimethylacrylate.
[0006] U.S. Pat. No. 2,948,666 and U.S. Pat. No. 5,605,936 disclose
processes for producing irradiated polypropylene. The latter
specification discloses the production of a high molecular weight,
non-linear propylene polymer material characterised by high melt
strength by high-energy irradiation of a high molecular weight
linear propylene polymer. It is disclosed that the ionising
radiation for use in the irradiation step may comprise electrons
beamed from an electron generator having an accelerating potential
of 500 to 4000 kV. For a propylene polymer material without a
polymerised diene content, the dose of ionising radiation is from
0.5 to 7 Mrad. For propylene polymer material having a polymerised
diene content, the dose is from 0.2 to 2 Mrad.
[0007] WO 00/56793 and WO 00/56794 describe the production of
polypropylene having long chain branches by irradiating propylene
with an electron beam. The beam has an energy of at least 5 Mev.
Irradiation is carried out in the presence of a grafting agent.
[0008] A particular class of cross-linked polyolefins are
vulcanised polyolefins. Vulcanisation, by reaction with sulphur or
other suitable agent under intense heat, leads to sulphur atoms
forming cross-links between polymer chains. This, in turn, leads to
an increase in cross-linking between the polyole fin chains and to
advantageous changes in physical properties.
[0009] In view of the above, ft will be appreciated that methods of
making non-linear polymers are not entirely satisfactory.
Specifically, it will be appreciated that the high-energy
irradiation used in many methods amounts to very harsh processing
conditions. Further, in the prior known methods using these very
harsh conditions, reticulation or vulcanisation is uncontrolled and
leads to a product having a large molecular weight distribution. As
such, it is desirable to provide further and preferably improved
methods of making non-linear polymers.
[0010] It is an object of the present invention to solve the
problems associated with the known processes, and to provide a new
method for making a non-linear polyolefin.
[0011] Accordingly, a first aspect of the present invention
provides a method for the production of a non linear polyolefin,
which method comprises:
[0012] (a) providing a polyolefin having a ratio of internal to
terminal double bonds of at least 1:1 and;
[0013] (b) forming a non-linear polyolefin from the polyolefin
provided in step (a).
[0014] A second aspect of the present invention provides a method
for the production of a functionalised polyolefin, which method
comprises:
[0015] (a) providing a polyolefin having a ratio of internal to
terminal double bonds of at least 1:1 and;
[0016] (b) forming a functionalised polyolefin from the polyolefin
provided in step
[0017] (a) by performing an addition reaction at one or more of the
double bonds.
[0018] A third aspect of the present invention provides a method
for the production of a polyolefin foam, which method
comprises:
[0019] (a) providing a polyolefin having a ratio of internal to
terminal double bonds of at least 1:1 and;
[0020] (b) forming a polyolefin foam from the polyolefin provided
in (a).
[0021] A fourth aspect of the present invention provides a
non-linear polyolefin obtainable according to the method as defined
in the first aspect of the present invention.
[0022] A fifth aspect of the present invention provides a
functionalised polyolefin obtainable by the method as defined above
in the second aspect of the present invention.
[0023] A sixth aspect of the present invention provides a
polyolefin foam obtainable according to the method as defined in
the third aspect of the present invention.
[0024] A seventh aspect of the present invention provides a
polyolefin having a ratio of internal to terminal double bonds of
at least 1:1.
[0025] An eighth aspect of the present invention provides the use
of a polyolefin as defined in the seventh aspect of the present
invention for making a non-linear polyolefin, a functionalised
polyolefin, or a polyolefin foam as defined in the first, second
and third aspects of the present invention.
[0026] A ninth aspect of the present invention provides a method
for the production of a polyolefin which method comprises a step
of:
[0027] polymerising an olefin monomer in the presence of a catalyst
component having formula (1): R''(Cp)(C'p)MQp (1) wherein Cp is a
cyclopentadienyl group having at least one substituent that is
positioned distal to the bridge; Cp' is an unsubstituted or 3-
and/or 6-substituted fluorenyl group; R'' is a structural bridge
imparting stereorigidity to the catalyst; M is a metal atom from
Group 4, 5 or 6 of the Periodic Table; and each Q is a hydrocarbyl
group having from 1 to 20 carbon atoms and p is the valence of M
minus 2; under polymerising conditions to form a polyolefin,
characterised in that the olefin monomer is present at a
concentration of less than 3 M/L, and polymerisation is carried out
a temperature in the range of from 20 to 90.degree. C. so that the
formed polyolefin has a ratio of internal to terminal double bonds
of at least 1:1.
[0028] The polyolefin that is provided in step (a) of the methods
according to the first, second and/or third aspects of the present
invention advantageously may be as defined in the seventh aspect of
the present invention. Further, in one embodiment, the method
according to the ninth aspect of the present invention may be used
to produce the polyolefin that is provided in step (a) of the
methods according to the first, second and/or third aspects of the
present invention.
[0029] For the purposes of the present invention the term
`non-linear polyolefin` is intended to encompass cross-inked
polyolefins as well as polyolefins having long chain branching
(LCB). In the context of the present invention, long chain means
branches comprising 20 carbon atoms or more. It is preferred that
the branches comprise from 20-100,000 carbon atoms, more preferably
from 100-100,000 carbon atoms and most preferably from 100-10,000
carbon atoms.
[0030] The present invention has arisen from the present inventors
studies of the molecular weight of polyolefins produced using a
catalyst having formula (1) as set out above. The present inventors
measured the molecular weight of the polyolefin products with
reference to melt index and also by gel permeation chromatography
and by viscosity measurements.
[0031] It is known that a high melt index indicates a low molecular
weight and that a low melt index indicates a high molecular weight.
In the case of the products formed using a catalyst having formula
(1), the melt index indicated a high molecular weight. However,
surprisingly, gel permeation chromatography measurements indicated
a much lower molecular weight. The present inventors now can
explain t his discrepancy. The high molecular weight indicated by
the melt index corresponds to the molecular weight of the
polyolefin including a non-linear polyolefin component. The
non-linear component is formed as a result of `cross-links` formed
between sites of unsaturation in the polymer chain under the high
temperature conditions at which melt index is measured. The non
linear component is formed only because of the high ratio of
internal to terminal double bonds in the polyolefin produced using
the catalyst of formula (1). This non-linear component is filtered
out during gel permeation chromatography measurements so that gel
permeation chromatography measures only the molecular weight of the
linear component.
[0032] The polyolefins having the high ratio of into mal to
terminal double bonds are hitherto unknown and, thus, form the
basis for the present invention. The method according to the first
aspect produces polyolefins that advantageously can undergo a
variety of subsequent reactions to form further useful products
such as non-linear polyolefins and functionalised polyolefins.
[0033] The method according to the first aspect produces non-linear
polyolefins having desirable mechanical and physical processing
capabilities. In particular, the method produces non-linear
polyolefins with desirable melt strength and processing
capabilities. Further, the method produces non-linear polyolefins
having a desirable narrow molecular weight distribution, for
example, a molecular weight distribution of up to about 5.
[0034] The melt strength of non-linear polyolefins produced
according to the first aspect desirably may be at least 1.5 times,
or even twice, the melt strength of the corresponding linear
polyolefin. For example, the melt strength of the non-linear
polyolefins may be .gtoreq.12, or even .gtoreq.16.
[0035] Preferably, in one embodiment of the first aspect, the
non-linear polyolefin is a cross-linked polyolefin. In another
embodiment, preferably, the non-linear polyolefin is a polyolefin
having LCB. Optionally, the polymer having LCB al so is
cross-linked.
[0036] Where the non-linear polyolefin is a cross-linked
polyolefin, it may be vulcanised.
[0037] The step of forming the non-linear polyolefin in step (b) in
the method according to the first aspect is not especially limited.
Because of the chemical reactivity of the internal double bonds of
the polyolefin provided in step (a), in step (b), it is possible to
create long chain branching and/or cross-linking.
[0038] Cross-inking is achievable in step (b) by controlled
reticulation of polyolefin chains. This may be contrasted with
reticulation by irradiation in the prior art that is uncontrolled.
Typically, reticulation will be free-radical induced. Thus, in one
embodiment, step (b) preferably comprises a step of inflating
cross-linking using a free-radical inducing agent. Cross-linking
also may be induced by low dose radiation. This provides the
possibility for forming the cross-linked polyolefins according to
this invention having improved mechanical and physical
properties.
[0039] Preferably, the free-radical inducing agent is oxygen or
heat. The conditions under which step (b) is carried out in the
method according to the first aspect are not especially limited
provided that long chain branch or reticulation (cross-linking) is
favoured.
[0040] In one embodiment, a polypropylene having a ratio of
internal to terminal double bonds of at least 1:1 can be processed
in accordance with WO 00/56794, the contents of which are
incorporated herein by reference. The polypropylene is mixed with a
grafting agent and then irradiated. The grafting agent increases
the long chain branching of the propylene molecules as a result of
the irradiation. The grafting agent is directly incorporated into
the polypropylene molecule during the irradiation step. A
particularly preferred grafting agent comprises tetravinylsilane.
The accelerating potential or energy of the electron beam is at
least 5 MeV, more preferably from 5 to 10 MeV. The power of the
electron beam generator is preferably from 50 to 500 Kw. The
radiation dose to which to which the propylene/grating agent
mixture is subjected is preferably 5 to 100 kGray.
[0041] Where the non-linear polyolefin formed in step (b) is a
vulcanised polyolefin, the conditions under which step (b) is
carried out must favour vulcanisation. Such conditions are, for
instance by reaction with sulphur or other suitable agent under
intense heat.
[0042] As mentioned above, step (a) may include a step of producing
the polyolefin having a ratio of internal to terminal double bonds
of at least 1:1. In this regard, this polyolefin may be produced in
accordance with any embodiment of the ninth aspect of the present
invention as defined above. Polymerising in step (a) can be carried
out first under polymerisation conditions, and then step (b) can be
carried out subsequently under different conditions.
[0043] Preferably, step (a) is carried out in a first reaction zone
and step (b) is carried out in a second reaction zone. In a
preferred embodiment of the present method, the first reaction zone
is in series with the second reaction zone.
[0044] In the fourth aspect of the present invention, the
non-linear polyolefin (which is obtainable by the method according
to the first aspect of the present invention) preferably comprises
a non-linear polypropylene and/or a non-linear polyethylene. The
non-linear polyolefins according to the fourth aspect of the
present invention have increased melt strength. This particular
rheological property provides an outstanding processing behaviour
which allows the non-linear polyolefins produced in accordance with
the invention to be suitable particularly for producing films,
sheets, fibres, pipes, foams, hollow articles, panels and coatings.
The non-linear polyolefins also have improved mechanical
properties, such as flexural modulus and impact resistance.
[0045] Preferably, in one embodiment, the non-linear polyolefin is
a cross-linked polyolefin, more preferably a vulcanised polyolefin.
In another embodiment, the non-linear polyolefin preferably is a
polyolefin having long chain branching. Optionally, the polyolefin
having long chain branching also is cross-linked.
[0046] The method according to the second aspect produces
functionalised polyolefins according to the fifth aspect of the
present invention. The functionalised polyolefins have new
mechanical and physical properties. Functional groups are
introduced into the polymer chain by addition reactions across the
double bonds.
[0047] Desirable functional groups include polar groups such as
carboxylic acid groups, acrylic groups, acrylate groups and esters
of carboxylic acids. These functional groups facilitate lamination
of the polymer chain with other polymers. Thus, these
functionalised polyolefins are suitable for use in making paints
and for printing and laminating applications.
[0048] In one embodiment of the third aspect of the present
invention, the polyolefin provided in step (a) may be produced in
accordance with the method according to the ninth aspect of the
present invention. Preferably, the polyolefin is polypropylene or
polyethylene.
[0049] Preferably, step (a) in the method according to the third
aspect of the present invention, comprises producing a polyolefin
having a ratio of internal to terminal double bonds of at least
1:1. In this embodiment, producing the polyolefin in step (a) and
forming the polyolefin foam in step (b) may be carried out in
separate reaction zones. Preferably, step (a) is carried out in a
first reaction zone and step (b) is carried out in a second
reaction zone in series with the first reaction zone.
[0050] A sixth aspect of the present invention provides a
polyolefin foam, obtainable by the method according to the third
aspect of the present invention. Preferably, the polyolefin foam is
formed from a cross-linked polyolefin. The size and uniformity of
bubbles in the formed polyolefin foam are dictated to some extent
by the melt strength of the starting material. Therefore, where the
polyolefin foam is formed from a crosslinked polyolefin having an
improved melt strength (as is obtainable by the first aspect of the
present invention), this leads to a polyolefin foam that is light
with good mechanical properties.
[0051] In the seventh aspect of the present invention, the
polyolefin is obtainable by the method according to the ninth
aspect of the present invention. Preferably, the polyolefin has
more internal double bonds than terminal double bonds. More
preferably, the ratio of internal to terminal double bonds is 2:1
or higher, still more preferably 2.5:1 or higher, even more
preferably 5:1 or higher, most preferably 6:1 or higher.
[0052] Also preferably, the polyolefin is polypropylene or
polyethylene. In this regard, the polypropylene or polyethylene may
be a homopolymer or copolymer of polypropylene or polyethylene.
Homopolypropylene, homopolyethylene and copolymers of ethylene with
butane and hexene are particularly preferred.
[0053] A copolymer of ethylene with hexene will contain more
internal double bonds than homopolyethylene.
[0054] In the case of polypropylene, all internal double bonds and
also all chain end double bonds have been observed to be vinylidene
double bonds.
[0055] Typically, the polyolefin produced in the method according
to the ninth aspect of the present invention is a linear
polyolefin.
[0056] Preferably, the polyolefin produced in the method according
to the ninth aspect is a polypropylene or polyethylene. In this
regard, the polypropylene or polyethylene may be a homopolymer or
copolymer of polypropylene or polyethylene. Homopolypropylene,
homopolyethylene and copolymers of ethylene with butene and hexene
are particularly preferred.
[0057] In any embodiment of the method according to the ninth
aspect, the polyolefin preferably has more internal double bonds
than terminal double bonds. More preferably, the ratio of internal
to terminal double bonds is 2:1 or higher, still more preferably
2.5:1 or higher, even more preferably 5:1 or higher, most
preferably 6:1 or higher.
[0058] The particular metallocene catalyst used in the polymerising
step leads to the advantages of the present method. The particular
symmetry of the catalyst component can produce a polyolefin having
a ratio of internal to terminal double bonds of at least 1:1. This
provides an important fraction of the vinyl groups in the backbone
of the polymer.
[0059] Without wishing to be bound by theory, a discussion of
mechanisms for the formation of internal unsaturations in propane
polymerisation can be found in `Organometallics` 2001, 20,
1918-1931.
[0060] It can be seen that the mechanism for the formation of
internal double bonds can be contrasted with a .beta.-hydrogen
elimination or .beta.-alkyl elimination, which results in a
terminal double bond. ##STR1##
[0061] However, with reference to FIG. 1 of the cited document, it
can be seen that the ratio of internal to terminal double bonds is
clearly below 1. This may be derived from "a" which reflects the
terminal vinylidenes and "a+d" that reflects the sum of the
terminal vinylidenes (one H) and the intern al vinylidenes (two
H).
[0062] A ratio of internal to terminal double bonds that is lower
than 1 can also be observed in Table II of the cited
Organometallics publication by summing all terminal double
bonds.
[0063] ACS Symp. Ser. 2000, 760, 174-93 reports a study on
propylene polymerisation with a chiral, C.sub.2-symmetric
zirconocene catalyst. The article reports a .sup.1H NMR analysis of
the olefin and saturations in the polymer product. On page 3 lines
3 to 4 it is stated that the allyl end group always prevails over
the others. As such, the polymers produced are not in accordance
with the present invention where the polymers must have a ratio of
internal to terminal double bonds of at least 1:1.
[0064] The preferred structure of the catalyst component having
formula (1) and in particular the ligands of the catalyst will be
discussed in more detail below.
[0065] Where present, preferably, each substituent on Cp or Cp'
Independently comprises a group selected from an aryl having from
1-20 carbon atoms, a hydrocarbyl having from 1-20 carbon atoms, a
cycloalkyl, a silane, an alkoxy and a halogen. More preferred
substituents include alkyl, phenyl (Ph), benzyl (Bz), naphthyl
(Naph), indenyl (Ind) and benzindenyl (Bzind), silane derivatives
(e.g. Me.sub.3Si), alkoxy (preferably R--O, where R is
C.sub.1-C.sub.20 alkyl), cydoalkyl, and halogen. The most preferred
substituents are n-Pr, i-Pr, n-Bu, t-Bu, Me, Et and Me.sub.3Si.
[0066] Preferred substituents on Cp' are selected from Me.sub.3Si,
Me, and t-Bu. A particularly preferred substituent on CP' is
t-Bu.
[0067] The substitution pattern of Cp and Cp' will be determined to
some extent by the desired polymer product, for example whether a
syndiotactic or isotactic product is desired. In this regard, a
C.sub.1 symmetric metallocene is required to make an isotactic
polypropylene. Accordingly, provided that the metallocene has the
desired symmetry, Cp may be mono-, di- or tri-substituted and Cp'
may be unsubstituted or mono- or di-substituted.
[0068] As mentioned above, Cp has at least one substituent that is
positioned distal to the bridge. Any further substituents on Cp may
be positioned vicinal or proximal to the bridge. A preferred
further substituent on Cp is Me. A particularly preferred distal
substituent on Cp is t-Bu.
[0069] In one embodiment, preferably, Cp is a monosubstituted
cyclopentadienyl group and Cp' is an unsubstituted fluorenyl
group.
[0070] The metal, M, in the metallocene catalyst typically is Ti,
Zr, Hf, or V and preferably Zr. Q is preferably a halogen;
typically Cl. Typically the valence of the metal is 4, such that p
is 2.
[0071] The type of bridge present between the rings in the
above-described catalyst is not itself particularly limited.
Typically R'' comprises an alkylidene group having 1 to 20 carbon
atoms, a germanium group (e.g. a dialkyl germanium group), a
silicon group (e.g. a dialkyl silicon group), a siloxane group
(e.g. a dialkyl siloxane group), an alkyl phosphine group or an
amine group. Preferably, the substituent comprises a silyl radical
or a hydrocarbyl radical having at least one carbon atom to form
the bridge, such as a substituted or unsubstituted ethylenyl
radical (e.g. --CH.sub.2CH.sub.2--). Most preferably R'' is
isopropylidene (Me.sub.2C), Ph.sub.2C, ethylenyl, or Me.sub.2Si. It
is particularly preferred that the catalyst comprises a Me.sub.2C,
Ph.sub.2C, or Me.sub.2Si bridge.
[0072] The most preferred catalyst component of the present
invention is a catalyst component of formula (1) where Cp' is an
unsubstituted fluorenyl group and Cp is a monosubstituted
cydopentadienyl group where the substituent is preferably bulky
(e.g. .sup.tBu) and is positioned distal to the bridge. An example
is shown below:
[0073] Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2
[0074] The catalyst system of the present invention is not
particularly limited provided that it comprises at least one
metallocene catalyst component as defined above. Thus the system
may comprise further catalysts, if necessary, such as further
metallocene catalysts.
[0075] The catalyst system of the present invention typically
comprises, in addition to the above catalyst component, one or more
activating agents capable of activating the metallocene catalyst
component. Typically, the activating agent comprises an aluminium-
or boron-containing activating agent. Boron-containing activating
agents are particularly preferred.
[0076] Suitable aluminium-containing activating agents comprise an
alumoxane, an alkyl aluminium compound and/or a Lewis acid.
[0077] The alumoxanes that can be used in the present invention are
well known and preferably comprise oligomeric linear and/or cyclic
alkyl alumoxanes represented by the formula (A): ##STR2## for
oligomeric linear alumoxanes; and formula (B) ##STR3## for
oligomeric cyclic alumoxanes, wherein n is 1-40, preferably 10-20;
m is 3-40, preferably 3-20; and R is a C.sub.1-C.sub.8 alkyl group,
preferably methyl. Generally, in the preparation of alumoxanes
from, for example, aluminium trimethyl and water, a mixture of
linear and cyclic compounds is obtained.
[0078] The amount of alumoxane and metallocene usefully employed in
the preparation of a solid support catalyst can vary over a wide
range. Generally the aluminium to transition metal mole ratio is in
the range between 1:1 and 100:1, preferably in the range 5:1 and
80:1 and more preferably in the range 5:1 and 50:1.
[0079] When Q in general formula (1) includes a alkyl group,
preferred activating agents include hydroxy isobutylaluminum and
metal aluminoxinates. These are particularly, preferred for
metallocenes as described in Main Groups Chemistry, 1999, Vol. 3,
pg. 53-57; polyhedron 18 (1999) 2211-2218; and Organometallics
2001, 20, 460-467.
[0080] Suitable boron-containing activating agents may comprise a
triphenylcarbenium boronate, such as
tetrakis-pentafluorophenyl-borato-triphenylcarbenium as described
in EP-A-0427696: ##STR4## or those of the general formula below, as
described in EP-A-0277004 (page 6, line 30 to page 7, line 7):
##STR5##
[0081] The activating agent preferably is of the type MAO and more
preferably it is a boron-based activator.
[HMe.sub.2N(C.sub.6H.sub.5)][B(C.sub.6F.sub.5).sub.4/Al(.sup.tBu).sub.3
is most preferred.
[0082] The conditions under which the polymerising step is carried
out are not especially limited provided that the formation of a
polyolefin backbone having a ratio of internal to terminal double
bonds of at least 1:1 is favoured.
[0083] The monomer is present at a comparatively low concentration
in step (a) (i.e. not bulk monomer). Preferably, the monomer is
present at a concentration of less than 2 mol/L, even more
preferably less than 1 mol/L.
[0084] Polymerisation preferably is carried out at a temperature in
the range of from 20.degree. C. to 100.degree. C., more preferably
at a temperature in the range of from 30.degree. C. to 90.degree.
C., even more preferably at a temperature in the range of from
60.degree. C. to 80.degree. C.
[0085] The catalyst system of the present invention may be employed
in any polymerisation method such as a slurry polymerisation, a
solution polymerisation, or a gas phase polymerisation, provided
that the required catalytic activity is not impaired. In a
preferred embodiment of the present invention, the catalyst system
is employed in a solution polymerisation process, which is
homogeneous, or a slurry process, which is heterogeneous.
[0086] In a solution process, typical solvents include hydrocarbons
having 4-7 carbon atoms such as heptane, toluene or
cyclohexane.
[0087] Typical polymerisation conditions in a slurry polymerisation
include polymerisation at a pressure of from 0.1-5.6 MPa and a
reaction time of from 10 mins to 4 hours. In a slurry process it is
necessary to immobilise the catalyst system on an inert support,
particularly a porous solid support such as talc, inorganic oxides
and resinous support materials such as polyolefin. Preferably, the
support material is an inorganic oxide in its finely divided
form.
[0088] Suitable inorganic oxide materials, which are desirably
employed in accordance with this invention, include group IIA,
IIIA, IVA, or IVB metal oxides such as silica, alumina and mixtures
thereof. Other inorganic oxides that may be employed either alone
or in combination with the silica, or alumina are magnesia,
titania, zirconia, and the like. Other suitable support materials,
however, can be employed, for example, finely divided
functionalised polyole fins such as finely divided
polyethylene.
[0089] Preferably, the support is a silica support having a surface
area of from 100-1000 m.sup.2/g, more preferably from 200-700
m.sup.2/g, and a pore volume of from 0.5-4 ml/g, more preferably
from 0.54 ml/g.
[0090] The order of addition of the catalyst component and
activating agent to the support material can vary. In accordance
with a preferred embodiment of the present invention, activator
dissolved in a suitable inert hydrocarbon solvent is added to the
support material slurried in the same or other suitable hydrocarbon
liquid and thereafter the catalyst component is added to the
slurry.
[0091] Preferred solvents include mineral oils and the various
hydrocarbons which are liquid at reaction temperature and which do
not react with the individual ingredients. Illustrative examples of
the useful solvents include the alkanes such as pentane,
iso-pentane, hexane, heptane, octane and nonane; cycloalkanes such
as cyclopentane and cyclohexane, and aromatics such as benzene,
toluene, ethylbenzene and diethylbenzene.
[0092] Preferably the support material is slurried in toluene and
the catalyst component and alumoxane are dissolved in toluene prior
to addition to the support material.
[0093] In one preferred embodiment, the catalyst system is not
immobilised on an inert support.
[0094] The molecular weight of the polyolefin backbone formed in
the method according to the ninth aspect is not especially limited.
Typically, the backbone has a medium molecular weight, such as of
from 100,000 to 1,000,000. Preferably the molecular weight of the
backbone is from 300,000 to 500,000 and most preferably is about
400,000. Advantageously, it has been found that the molecular
weight distribution of the polyolefin formed in the method
according to the ninth aspect of the present Invention has a narrow
molecular weight distribution, preferably less than 6, more
preferably less than 4, still more preferably of about 2.
[0095] The polyolefins produced by the method according to the
ninth aspect are not particularly limited provided that the
polyolefin product has a ratio of internal to terminal double bonds
of at least 1:1. It is observed that the nature of the activating
agent has an influence on the proportion of internal vinilydene
unsaturations with respect to the total amount of unsaturations as
can be seen in FIG. 5.
[0096] It is particularly preferred that polyolefin is polyethylene
and/or polypropylene.
[0097] A tenth aspect of the present invention provides the use of
a catalyst having formula (1) as defined in relation to the ninth
aspect of the present invention for the preparation of a polyolefin
having a ratio of internal to terminal double bonds of at least 1:1
as described above in relation to the seventh aspect of the present
invention or for the preparation of a non-linear polyolefin as
defined above in relation to the first aspect of the present
invention or a functionalised polyolefin as defined above in
relation to the second aspect of the present invention or a
polyolefin foam as defined in relation to the third aspect of the
present invention.
[0098] Preferably, in the tenth aspect of the present invention,
the polyolefin is polyethylene or polypropylene. More preferably,
the non-linear polyolefin is a cross-linked polyolefin or a
polyolefin having long chain branching (optionally also
cross-linked) as defined above in relation to the fourth aspect of
the present invention.
LIST OF FIGURES
[0099] FIG. 1 represents the 150 MHz .sup.13C NMR spectrum of
polypropylene sample number 11 of Table 1, prepared with the
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2/HMe.sub.2N(C.sub.6H.sub.5)][B(C.s-
ub.6F.sub.5).sub.4]/Al(.sup.tBu).sub.3 catalyst system at a
temperature of 70.degree. C.
[0100] FIG. 2 represents a possible formation mechanism for
internal double bonds.
[0101] FIG. 3 represents the olefinic region of the 600 MHz .sup.1H
NMR spectrum of the same polypropylene sample number 11 of Table 1
as in FIG. 1, wherein v.sub.d represents the internal vinylidene,
v.sub.d represents the terminal vinylidene and * represents the
anti-oxidant.
[0102] FIG. 4 represents a plot of the viscosity determined
molecular weight as a function of monomer concentration for
polypropylene samples polymerised in the presence of
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2 and activated with
methylalumoxane (MAO), at a temperature of 70.degree. C.
[0103] FIG. 5 represents the .sup.1H NMR spectra in the olefinic
region of 400 MHz to polypropylene samples prepared with
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2 and different activating
agents, respectively methylalumoxane, a mixture of methylalumoxane
and PhO and a mixture of
[HMe.sub.2N(C.sub.6H.sub.5)][B(C.sub.6F.sub.5).sub.4] and
triisobutylaluminum (TIBAL)
[0104] The invention will now be described in further detail by way
of example only, with reference to the following non-limiting
specific embodiments.
EXAMPLES
Propene Homopolymerization Promoted by
Me.sub.2C(3-.sup.tBu-C)(Flu)ZrCl.sub.2-Based Catalyst Systems.
[0105] Propene was polymerised in the presence of
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2, activated with either
methylalumoxane (MAO) or
HMe.sub.2N(C.sub.6H.sub.5)][B(C.sub.6F.sub.5).sub.4]/Al(.sup.tBu).sub.3,
respectively at the temperatures of 30.degree. C. and of 70.degree.
C., and at concentrations of propene ([C.sub.3H.sub.6]) of from 0.3
to 7.5 mol/L. A list of the polymerisation runs is given in Table
1. TABLE-US-00001 TABLE 1 Activating T [C.sub.3H.sub.6] [Zr]
.times. 10.sup.5 [Al] .times. 10.sup.2 [B] .times. 10.sup.5 t Y
Sample agent (.degree. C.) (mol/L) (mol/L) (mol/L) (mol/L) (min)
(g) 1 MAO 30 0.74 .+-. 0.06 2.9 3.9 -- 30 6.2 2 1.30 .+-. 0.06 1.8
3.6 -- 30 7.6 3 2.48 .+-. 0.06 0.8 3.6 -- 30 7.1 4 5.02 .+-. 0.12
0.5 3.6 -- 20 8.2 5 7.32 .+-. 0.12 1.5 3.0 -- 56 33.1 6 70 0.36
.+-. 0.03 4.1 3.9 -- 120 0.3 7 0.73 .+-. 0.07 3.6 4.2 -- 120 1.7 8
1.33 .+-. 0.07 4.1 4.2 -- 20 6.7 9 2.64 .+-. 0.07 2.9 4.0 -- 10 6.9
10 6.70 .+-. 0.07 4.1 2.0 -- 60 4.4 11 [HMe.sub.2NPh] 70 0.63 .+-.
0.07 4.7 0.8 21 120 1.4 12 [B(C.sub.6F.sub.5).sub.4]/ 1.32 .+-.
0.07 3.4 0.8 6.5 60 3.0 13 Al('Bu).sub.3 2.77 .+-. 0.07 1.7 0.8 5.1
30 3.1 14 7.10 .+-. 0.10 3.4 1.6 11 6 12.1
[0106] The .sup.13C NMR spectra of all polypropylene samples
indicated a predominantly isotactic microstructure typical of site
control.
[0107] The .sup.13C NMR fraction on mmmm pentad (as a
semi-quantitative indication of the degree of isotacticity), the
mole fraction of stereoirregular monomeric units, x.sub.d
(estimated by statistical analysis of the .sup.13C NMR sequence
distribution), and the melting temperature and enthalpy, T.sub.m
and .DELTA.h.sub.m (measured by DSC on the 2.sup.nd heating scan)
are reported In Table 2, for each of the samples listed In Table 1.
TABLE-US-00002 TABLE 2 Activating T.sub.p [C.sub.6H.sub.6]
.DELTA.h.sub.m [.eta.] Sample agent (.degree. C.) (mol/L) [mmmm]
x.sub.d T.sub.m (.degree. C.) (J/g) (dL/g) 1 MAO 30 0.74 .+-. 0.06
0.86 0.030 137.7 87 0.25 2 1.30 .+-. 0.06 0.83 0.036 135.9 80 0.41
3 2.48 .+-. 0.06 0.83 0.036 132.9 73 0.70 4 5.02 .+-. 0.12 0.79
0.047 127.4 63 1.08 5 7.32 .+-. 0.12 0.77 0.050 125.9 67 0.95 6 70
0.36 .+-. 0.03 0.75 0.055 111.7 56 0.06 7 0.73 .+-. 0.07 0.79 0.046
120.4 62 0.09 8 1.33 .+-. 0.07 0.81 0.042 125.9 77 0.14 9 2.64 .+-.
0.07 0.81 0.042 129.4 75 0.20 10 6.70 .+-. 0.07 0.81 0.041 129.9 61
0.45 11 [HMe.sub.2NPh] 70 0.63 .+-. 0.07 0.75 0.057 126/140 33 0.15
12 [B(C.sub.6F.sub.5).sub.4]/ 1.32 .+-. 0.07 0.79 0.046 124/140 40
0.17 13 Al('Bu).sub.3 2.77 .+-. 0.07 0.81 0.041 125.2 59 0.24 14
7.10 .+-. 0.10 0.81 0.042 129.2 69 0.27
[0108] The thermal behaviour of the polymers produced is
intriguing. Indeed, for samples 11 to 14, the DSC melting
endotherms showed two maxima, one of which occurring at the fairly
high temperature of about 140.degree. C., and with a relative
intensity increasing with decreasing concentration in monomer
[C.sub.3H.sub.6].
[0109] As shown in FIG. 1, the .sup.13C NMR spectra of all polymers
(and particularly of t hose prepared at low monomer concentration)
show a plethora of weak peaks in addition to those arising from
stereo- and regloirregular units.
[0110] Parts of such peaks are due to chain end-groups. The origin
of the remaining .sup.13C NMR peaks was revealed by an examination
of the olefinic region in the .sup.1H NMR spectra represented in
FIG. 3, which shows a comparatively strong resonance at
.delta.=4.73 ppm, overlapping the lower-field component of the 1:1
"doublet" (.delta.=4.66 and 4.73 ppm) of the geminal protons in
terminal vinylidenes. This pattern is typical of polypropylene
samples containing also "internal" vinylidenes, whose origin is
explained in terms of an "allylic" activation of the growing chain
as represented in FIG. 2.
[0111] The results shown in FIG. 3 may be contrasted with those
shown in FIG. 1 of "Organometallics" 2001, 20, 1918-1931 discussed
above. In FIG. 3, Vd' reflect the terminal vinylidene and "Vd+Vd'"
reflects the sum of the terminal vinylidene and the internal
vinylidene. Quite clearly, in FIG. 3, the ratio of internal to
terminal double bonds is well above 1.
[0112] Minor amounts of internal vinylidenes have been detected
previously in polypropylenes prepared with a variety of
anse-metallocenes, and in special cases (e.g., sterically crowded
rac-C.sub.2-symmetric ansa-zirconocenes, such as
rac-Me.sub.2C(3-.sup.tBu-1-lnd).sub.2ZrCl.sub.2) they can approach
the action of terminal ones. However, the ratio between internal
and terminal vinylidenes of about 2.5, measured in polypropylene
samples prepared according to the pre sent invention at a
temperature of 70.degree. C. and at low propene concentration with
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2, preferably activated with
[HMe.sub.2N(C.sub.6H.sub.5)]
[B(C.sub.6F.sub.5).sub.4]/Al(.sup.tBu).sub.3, is totally unexpected
and unprecedented.
[0113] Also notable is the almost complete absence of an y other
kind of olefinic unsaturations as seen on FIG. 3. The D isotope
effect has been measured by comparing the content of unsaturations
in samples of poly(propene-d.sub.0) and poly(propene-3,3,3-d.sub.3)
prepared at 70.degree. C. with the catalyst system
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2[HMe.sub.2N(C.sub.6H.sub.5)][B(C.s-
ub.6F.sub.5).sub.4]/Al(.sup.tBu).sub.3 under identical experimental
conditions. The ratio between internal and terminal vinylidenes
turned out to be higher in poly(propene-d.sub.0) and it must be
noted that the two samples have practically identical
stereoregularity.
[0114] Without wishing to be bound by theory, one can speculate
that, due to the high steric hindrance at the metal centre of a
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrP.sup.+ cation, following an
intramolecular event of .beta.-H transfer to Zr, double bond
rotation and re-insertion into the Zr--H bond with formation of a
Zr--C(Me).sub.2(P).sup.+ intermediate is unlikely, and either the
terminally unsaturated chain is released, or allylic activation
occurs with H.sub.2 evolution and formation of an internal
vinylidene as seen on FIG. 2.
[0115] The mole fractions of terminal and internal vinylidenes,
measured by .sup.1H NMR, in samples of poly(propene-d.sub.0) and
poly(propene-3,3,3-d.sub.3) prepared at 70.degree. C. with catalyst
system
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2/[HMe.sub.2N(C.sub.6H.sub.5-
)][B(C.sub.6F.sub.6).sub.4/Al(.sup.tBu).sub.3 under identical
experimental conditions are displayed in Table 3. TABLE-US-00003
TABLE 3 Poly(propene-d.sub.0) Poly(propene-3,3,3-d.sub.3) terminal
vinylidene (mol %) 1.0 1.1 internal vinylidene (mol %) 2.3 1.3
[0116] It was further observed that when the propene concentration
was increased, the mole fractions of both terminal and internal
vinylidenes decreased. This behaviour is displayed In Table 4
representing the mole fractions of terminal and internal
vinylidenes in polypropylene samples prepared with
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2/MAO at 70.degree. C., as
measured by .sup.1H NMR
[0117] It is speculated that, for the investigated catalyst,
.beta.-H transfer and allylic activation are mainly intramolecular
and not monomer-assisted, possibly due to the fact that the bulky
.sup.tBu substituent on the Cp ring hinders the formation of steric
ally demanding activated complexes. TABLE-US-00004 TABLE 4
[C.sub.3H.sub.6] terminal vinylidene internal vinylidene Sample
(mol/L) (mol %) (mol %) 6 0.36 0.65 0.53 9 2.64 0.26 0.19
[0118] With specific reference to .beta.-H transfer, the above
conclusion is consistent with the observed linear dependence of the
viscosity determined molecular weight M, on monomer concentration
([C.sub.3H.sub.6]) for the series of polymers prepared with
Me.sub.2C(3-.sup.tBu-Cp)(Flu)ZrCl.sub.2/MAO at 70.degree. C. and
displayed in FIG. 4. It indicates that the cumulative rate of the
active chain transfer pathways is independent of monomer
concentration ([C.sub.3H.sup.6]). The viscosity determined
molecular weight of the polymer M.sub.v is directly proportional to
(viscosity).sup.n where n is a constant that is characteristic of
the polymer.
[0119] Polypropylene samples were prepared with
Me2C(3-tBu-Cp)(Flu)ZrCl2 and different activating agents:
[0120] 1) MAO;
[0121] 2) a mixture MAO/PhO; and
[0122] 3) a mixture
[HMe.sub.2N(C.sub.6H.sub.5)][B(C.sup.6F.sub.5)].
[0123] The polymerisation reactions were all carried out at a
temperature of 50.degree. C. and with [C.sub.3H.sub.6] 0.4 M in
toluene. The results are presented in FIG. 5. The polymers obtained
with activating agents 2) and 3) contain a striking predominance of
internal vinylidenes as represented by the singlet at .delta.=4.81
ppm as compared to the terminal vinylidenes represented by the
doublet at .delta.=4.74 and 4.81 ppm.
* * * * *